diff --git a/lib/mjit/codegen.rb b/lib/mjit/codegen.rb
index b04cb7b2fe..6ebefde860 100644
--- a/lib/mjit/codegen.rb
+++ b/lib/mjit/codegen.rb
@@ -16,13 +16,18 @@ module RubyVM::MJIT
     # @param asm [RubyVM::MJIT::X86Assembler]
     def leave(ctx, asm)
       assert_eq!(ctx.stack_size, 1)
+      # TODO: Check interrupts
 
-      # pop the current frame (ec->cfp++)
+      # Pop the current frame (ec->cfp++)
       asm.add(:rsi, C.rb_control_frame_t.size) # rsi = cfp + 1
       asm.mov([:rdi, C.rb_execution_context_t.offsetof(:cfp)], :rsi) # ec->cfp = rsi
 
-      # return a value
+      # Return a value
       asm.mov(:rax, [:rbx])
+
+      # Restore callee-saved registers
+      asm.pop(:rbx)
+
       asm.ret
       EndBlock
     end
diff --git a/lib/mjit/x86_assembler.rb b/lib/mjit/x86_assembler.rb
index be65644650..c6c0cc2e19 100644
--- a/lib/mjit/x86_assembler.rb
+++ b/lib/mjit/x86_assembler.rb
@@ -37,7 +37,7 @@ module RubyVM::MJIT
           imm: imm8(src_imm),
         )
       else
-        raise NotImplementedError, "add: not-implemented input: #{dst.inspect}, #{src.inspect}"
+        raise NotImplementedError, "add: not-implemented operands: #{dst.inspect}, #{src.inspect}"
       end
     end
 
@@ -102,7 +102,31 @@ module RubyVM::MJIT
           disp: src_offset,
         )
       else
-        raise NotImplementedError, "mov: not-implemented input: #{dst.inspect}, #{src.inspect}"
+        raise NotImplementedError, "mov: not-implemented operands: #{dst.inspect}, #{src.inspect}"
+      end
+    end
+
+    def push(src)
+      case src
+      # PUSH r64
+      in Symbol => src_reg if r64?(src_reg)
+        # 50+rd
+        # O: Operand 1: opcode + rd (r)
+        insn(opcode: 0x50 + reg_code(src_reg))
+      else
+        raise NotImplementedError, "push: not-implemented operands: #{src.inspect}"
+      end
+    end
+
+    def pop(dst)
+      case dst
+      # POP r64
+      in Symbol => dst_reg if r64?(dst_reg)
+        # 58+ rd
+        # O: Operand 1: opcode + rd (r)
+        insn(opcode: 0x58 + reg_code(dst_reg))
+      else
+        raise NotImplementedError, "pop: not-implemented operands: #{dst.inspect}"
       end
     end
 
diff --git a/lib/ruby_vm/mjit/compiler.rb b/lib/ruby_vm/mjit/compiler.rb
index ff0003c8bf..8a5614c081 100644
--- a/lib/ruby_vm/mjit/compiler.rb
+++ b/lib/ruby_vm/mjit/compiler.rb
@@ -58,8 +58,16 @@ module RubyVM::MJIT
 
     #  ec: rdi
     # cfp: rsi
+    #
+    # Callee-saved: rbx, rsp, rbp, r12, r13, r14, r15
+    # Caller-saved: rax, rdi, rsi, rdx, rcx, r8, r9, r10, r11
+    #
     # @param asm [RubyVM::MJIT::X86Assembler]
     def compile_prologue(asm)
+      # Save callee-saved registers used by JITed code
+      asm.push(:rbx)
+
+      # Load sp to a register
       asm.mov(:rbx, [:rsi, C.rb_control_frame_t.offsetof(:sp)]) # rbx = cfp->sp
     end
 
@@ -103,6 +111,9 @@ module RubyVM::MJIT
         asm.mov([:rsi, C.rb_control_frame_t.offsetof(:sp)], :rbx) # cfp->sp = rbx
       end
 
+      # Restore callee-saved registers
+      asm.pop(:rbx)
+
       asm.mov(:rax, Qundef)
       asm.ret
     end
@@ -115,6 +126,7 @@ module RubyVM::MJIT
       C.dump_disasm(from, to).each do |address, mnemonic, op_str|
         puts "  0x#{"%p" % address}: #{mnemonic} #{op_str}"
       end
+      puts
     end
   end
 end